The exhaust gas emitted from an internal combustion engine may include a heterogeneous mixture that may contain gaseous emissions such as carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NOx), and condensed phase materials (liquids and solids) that constitute particulate matter (PM). Transition and primary group metal catalysts typically coat a catalyst support along with substrates to provide an engine exhaust system the ability to convert some, if not all of these exhaust components into other compounds.
Exhaust aftertreament systems may include a three-way catalyst (TWC) and a particulate filter (PF). The TWC provides a passage for gaseous emissions to flow through and undergo oxidation and reduction reactions with the catalytic components. The TWC may not comprise a binding element, whereas the PF may comprise a binding element to capture PM.
Over time, the PF may become full and a regeneration operation may be used to remove trapped particulates. The regeneration involves increasing the temperature of the particulate filter to a relatively high temperature, such as above 600° C., in order to burn the accumulated particulates into ash.
A potential drawback with the regeneration process is ash accumulation subsequent to the regeneration process in spark-ignited engines. The high-exhaust temperatures of spark-ignited engines (e.g., 550° C.) vaporizes the water released after combustion, thereby disabling the ability for water to sweep the ash from the exhaust pathway. This is generally in contrast to diesel engines where the water is not vaporized due to lower exhaust temperatures (e.g., 90° C.) and is able to reduce the ash load. One example attempt to address ash build up includes injecting air to reduce ash accumulation, such as described in Sorensen et al. in U.S. Patent No. 2011/0120090. Therein, an oxygen injection is used to further burn an ash accumulation and remove it from the PF.
However, the inventors herein have recognized potential issues with such systems. As one example, an oxygen injection upstream of a PF may increase an exhaust gas temperature above a threshold that may degrade the filter. By injecting air to initiate a regeneration, the regeneration temperature may be more difficult to regulate and increase a PF temperature to a temperature in which the PF may be degraded.
In one example, the issues described above may be addressed by a method for inverting an exhaust aftertreatment housing of a disconnected exhaust passage end over end during vehicle operation. In this way, a purifying device in the housing may receive exhaust gas at opposite ends based on an inversion of the housing. The inversion may be achieved by operation of one or more electronically controlled actuators, such as a motor, via a vehicle control system responsive to sensed operating conditions.
As one example, a particulate filter may be located with the exhaust aftertreatment housing. The particulate filter may fluidly connect a first exhaust passage to a second exhaust passage, wherein the first passage is upstream of the second passage. A rotating arm may turn about a rotation axis via a motor thereby rotating the housing end over end about the axis and inverting the particulate filter. Exhaust gas from the engine flows in the same way to the housing, but due to the housing inversion, now flows through an opposite end of the particulate filter as compared to flow prior to the inversion. Therefore, accumulated ash on a backside of the filter may receive higher pressure exhaust gas following rotation of the filter, which may dislodge the ash and blow it out the filter.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.